What happened
On 25 June 2009, an ATR 72-202, registration G-BWDB, was preparing for a scheduled passenger flight from London Gatwick Airport to Guernsey. During the initial pushback from Stand 9, a collision occurred involving the aircraft's nose landing gear bay.
Following the incident, the commander ordered the ground crew to halt the pushback. To rectify the situation and comply with Air Traffic Control instructions, the commander directed the crew to tow the aircraft forward onto Taxiway M. The goal was to position the aircraft far enough back on the taxiway to allow for a subsequent pushback beyond Taxiway Z. During this repositioning maneuver, the tow bar made contact with one of the nose gear bay doors, causing the tow bar's shear pin to fail.
As a precaution, the commander shut down the engines, and all 36 passengers and baggage were returned to the terminal while maintenance personnel were called to assess the damage.
The investigation
The AAIB investigation focused on the mechanical cause of the contact between the tow bar and the aircraft. The inquiry established that the damage was concentrated on the right rear nose landing gear bay door, including the hinges and actuating linkages.
Investigators examined the tow bar and discovered that a release cable guide bracket, located at the top of the bar, had been bent approximately 45 degrees from its vertical position. This modification was undocumented and had likely occurred during a previous towing operation. Under normal circumstances, this bracket is positioned such that it remains clear of the bay doors regardless of the towing angle. However, in its deformed state, the bracket struck the door as the tow bar was turned to an angle of roughly 40 to 50 degrees from the aircraft's centerline.
Findings
- The primary cause of the incident was an undocumented modification to the tow bar caused by a bent release cable guide bracket.
- The deformed bracket exerted pressure on the nose bay door during the repositioning maneuver, leading to a failure along the hinge line.
- The impact also resulted in the failure of the tow bar's shear pin.
- There were no injuries to the 4 crew members or 36 passengers on board.